html,body{
    background-color: black;
    width: 100%;
    height: 100%;
}
.box1{
    width: 600px;
    height: 20px;
    border: 4px groove greenyellow;
    margin: auto;
    color: #fff;
    text-align: center
}
.box1-2{
    width: 600px;
    height: 20px;
    background-color: red;
    margin-bottom: 10px;
}
.box2{
    position: absolute;
    left:0;
    top:0;
    right:0;
    bottom: 0;
    margin: auto;
    width: 300px;
    height: 200px;
    text-align: center;
    background-color: lightgray;
    line-height: 50px;
    padding-top: 100px;
    display: none; 
    z-index: 1000;
}